After Holmes’ opinions in the Schenck trilogy, the law of the United States was this: you could be convicted and sentenced to prison under the Espionage Act if you criticized the war, or conscription, in a way that “obstructed” conscription, which might mean as little as convincing people to write and march and petition against it. This is the context of the “fire in a theater” quote that people so love to brandish to justify censorship.